Justification:Ctenochaetus striatus is widespread throughout the Indo-Pacific region. It is the most common and abundant reef fish in the Indo-Pacific. It is a targeted food fish in parts of its distribution (i.e., American Samoa and the Philippines). In American Samoa, studies have failed to detect any population declines through harvesting. There is no evidence of population declines at the global scale due to harvesting. It is found in several marine reserves in parts of its range and harvest management measures are in place in some areas of its distribution. It is therefore listed as Least Concern. We recommend continued monitoring of the species' population and harvest trends. In addition, monitoring of the fisheries and comparison between fisheries data and the life history of this species in areas where it is heavily fished.

Ctenochaetus striatus is widespread throughout the Indo-Pacific Region and is found from the Red Sea and coast of East Africa to Pitcairn Island and French Polynesia except the Marquesas, northwards to the Ryukyu and Ogasawara Islands, Japan and southwards to Elizabeth/Middleton Reefs and Rapa. It was recorded from Masirah Island, central coast of Oman (J. McIlwain unpub. data).

Ctenochaetus striatus is the most common surgeonfish at most localities where it occurs. In Moorea, French Polynesia, it was the most abundant fish on the reef and was frequently encountered (Rainey 2009) and the Acanthuridae was dominant on the barrier reef (2.30 ind. m-2) and on the outer slope (1.61 ind. m-2). On the barrier reef, this species accounted for 34% of the total density and 29% of the total density on the outer slope (Moussa 2009).

In American Samoa, it was the single most common species found in underwater surveys (Green 1996, 2002; Green et al. 2005; Whaylen and Fenner 2005). In Fagatale Bay it is a dominant species on the reef slope (Green et al. 1999). It occurred in 100% of all transects and accounted for 22% of total biomass around Tutuila Island, American Samoa (Sabater and Tofaeono 2007). In Tutuila, Aunuu, and Taema Banks, American Samoa, it accounted for 21.9% of total biomass and was the most dominant reef species (Sabater and Tofaeono 2006).This was confirmed as the most dominant species based on the index of relative dominance (Sabater and Tofaeono 2007).

In Guam, it is the most abundant Acanthurid species (29%) but only makes up 5% of the acanthurid fishery (Division of Aquatic and Wildlife Resources unpub. data, J. McIlwain unpub. data). In the outer islands of American Samoa, C. striatus accounted for 51% of the reef-associated catch (21.4 mt) (Craig 2008).

It is abundant throughout the Great Barrier Reef and reefs of tropical East Africa. It is the most common Acanthurid and most abundant moderate sized reef fish in the Society Islands (Randall and Clements 2001). In Aitutaki Lagoon, Cook Islands, it made up the bulk of the spearfishers' catch, accounting for 45% of the catch; it also dominated the visual census survey. Surgeonfishes as a family comprised 53% of the catch (Adams et al. 1996).

Visual census surveys along the Iboih coast, Weh Island, Indonesia recorded fish densities of 7 individuals/750 m2 at Pantai Sirkui and 19 individuals/750 m2 at Teluk Pelabuhan (Faculty of Mathematics and Natural Science 2007). It is common in Palawan, Philippines, Milne Bay Province, Papua New Guinea, and in Raja Ampat, Indonesia, usually seen in depths less than 10 m (Werner and Allen 2000; Palawan Council for Sustainable Development unpub. data; Allen 2003, 2003b). It was the most abundant surgeonfish recorded in the Calamianes Islands, Philippines (Werner and Allen 2000).

In Moorea, French Polynesia, SPOT satellite images allowed estimation of the surface area of fringing reef (1,076 ha), barrier reef (3,788 ha) and outer slop (493 ha). A total of 35,117,140 individuals were recorded in this area in fish visual surveys conducted from 1990-1993 (Lecchini et al. 2006). In the Nabq Managed Resource Protected Area, South Sinai, Egyptian Red Sea, mean abundances of C. striatus showed differences at various depths and between no-take zones (NTZ) and take zones (TZ). Abundance was greater in fished areas at 3 and 10 m depths, this can be attributed to a result of reduced predation or competition (Ashworth and Ormond 2005).

Ctenochaetus striatus is found in a variety of habitats from protected lagoons to ocean reefs (Randall 2001a). It often forms large grazing aggregations (G. Allen pers. comm. 2010).

The genus Ctenochaetus feed on fine detrital material. They whisk the sand or rocky substratum with their teeth and utilize suction to draw in the detrital material that consists of diatoms, small fragments of algae, organic material and fine inorganic sediment (Randall and Clements 2001). C. striatus has low levels of SCFAs (short chain fatty acids) (Clements and Choat 1995). Species of Ctenochaetus share the presence of a thick-walled stomach (Randall and Clements 2001); this character is significant with respect to the nutritional ecology of this genus (Choat et al. 2002b).

A study by Trip et al. (2008) showed that there are several distinct trends in age structure, growth rate and size across 15 sites that spanned 158º longitude and 40º latitude of the Indian and Pacific Oceans. In both oceans, fish live longer at higher latitudes; in addition, Indian Ocean populations tended to be shorter-lived than those in the Pacific Ocean. Growth rate and adult size did not differ between the two oceans, and were not related to temperature in either the Pacific or Indian Ocean.

Growth

C. striatus is characterized by rapid growth in the first year, followed by attainment of asymptotic size by the fifth year in all populations examined to date. An analysis of 15 populations of this species sampled across 83% of its longitudinal and 66% of its latitudinal range showed that asymptotic growth was consistent across locations and geographical scales (Trip et al. 2008). The maximum number of annuli recorded for this species was 32 to 35 (Choat and Axe 1996).

A study by Choat and Robertson (2002) show the following maximum age estimates from different locations of this species' range:

The sexes are separate among the acanthurids (Reeson 1983). Acanthurids do not display obvious sexual dimorphism, males assume courtship colour. In the GBR, both sexes have similar gonad indexes (J.H. Choat pers. comm. 2010). This species forms resident spawning aggregations. It can 'hitch-hike' on migrating streams of A. nigrofuscus in the Red Sea, where upon reaching the spawning site they break off from the larger A. nigrofuscus aggregation to form a separate aggregation of 50-100 individuals (Myrberg et al. 1988). In Palau (Robertson 1983) and Tahiti (Randall 1961a), late afternoon spawning aggregations numbered thousands of fish. It also pair spawns (Domeier and Colin 1997). It was also observed to form spawning aggregations on the Great Barrier Reef (Randall 1961a, Robertson 1983, Squire and Samoilys unpub.).

In the Red Sea, this species was observed to form spawning aggregations around a coral knoll on the most seaward edge in front of reefs with deep water from June-September (Myrberg et al. 1988). In Aldabra Atoll, it spawns on the outer reef edge of the channel from August-December, 4-7 days before the full/new moon. In Palau, it spawns on the outer reef edge from January-April, 4-7 days before the full/new moon (Randall 1983). In Society Island, it was observed to spawn in 50 ft deep passage with strong currents set to open sea and on reef edges 8-25 ft deep (Randall 1961a). Size at sexual maturity is 135 mm (Choat and Robertson 2002a).

Ctenochaetus striatus is captured for food and is taken mainly in nets and traps. It is also a minor component of the aquarium trade (Global Marine Aquarium Database accessed 19 March 2010). Prices online range from $39.95-$69.95 (L. Rocha pers. comm. 2010). It is captured by spearfishers in Aitutaki Lagoon, Cook Islands (Adams et al. 1996). It is targeted in subsistence fisheries species in the Solomons, American Samoa, and the Philippines. It is occasionally found in fish markets.

Ctenochaetus striatus is heavily fished in American Samoa, an overfished, collapsed fishery. There was no relationship found between fishing pressure and longevity, growth or adult size across sampling sites, among which fishing pressure on this species varied from intense to zero (Trip et al. 2008).The status of reef fisheries in American Samoa has commonly been reported as over-exploited, however, comparing patterns and trends from fishery independent surveys with fishery-dependent data showed a significant decline in shoreline fishing effort and a non-significant decrease in boat-based effort, resulting in constant catch landings and catch-per-unit effort. Concurrent with the decline in fishing effort and constant catch landing was an increase in fish abundance and biomass for the targeted families. The decrease in fishing pressure occurred during a period of rapid population growth, indicating non-dependence of the general population on fishing, reflecting the change in the social and economic dynamics within the territory (Sabater and Carroll 2009).

Craig et al. (2008) showed that the current harvests of the subsistence fishery in outer islands of American Samoa is similar to those in historic and prehistoric periods, indicating that the fishery is harvested at a sustainable level.

Surgeonfishes show varying degrees of habitat preference and utilization of coral reef habitats, with some species spending the majority of their life stages on coral reef while others primarily utilize seagrass beds, mangroves, algal beds, and /or rocky reefs. The majority of surgeonfishes are exclusively found on coral reef habitat, and of these, approximately 80% are experiencing a greater than 30% loss of coral reef area and degradation of coral reef habitat quality across their distributions. However, more research is needed to understand the long-term effects of coral reef habitat loss and degradation on these species' populations. Widespread coral reef loss and declining habitat conditions are particularly worrying for species that recruit into areas with live coral cover, especially as studies have shown that protection of pristine habitats facilitate the persistence of adult populations in species that have spatially separated adult and juvenile habitats (Comeros-Raynal et al. 2012).

There are no species-specific conservation measures in place for this species. However, its distribution overlaps several marine protected areas within its range. In Samoa, SCUBA fishery has been banned since 2001 by Executive Order and subsequently in 2002 by regulation (Green 2003). Night spearfishing has been banned as well (J.H. Choat pers. comm. 2010). In Queensland, Australia, there is a recreational catch limit of 5 per species and a minimum size limit of 25 cm (Department of Primary Industries accessed 8 April 2010).

Faculty of Mathematic and Natural Science (FMIPA) University of Syiah Kuala. 2007. Community-drive coral conservation in Aceh, Indonesia. A Report to Rufford Small Grant (for Nature Conservation). The Rufford Small Grants Foundation.

Green, A.L. 1996. Status of the Coral Reefs of the Samoan Archipelago. Report to the Department of Marine and Wildlife Resources, Government of American Samoa, American Samoa.

Green, A.L. 2002. Status of Coral Reefs on the Main Volcanic Islands of American Samoa: A Re-survey of Long-Term Monitoring Sites (Benthic Communities, Fish Communities, and Key Macroinvertebrates). Report to the Department of Marine and Wildlife Resources, Pago-Pago, American Samoa.

Robertson, D.R. 1983. On the spawning behavior and spawning cycles of eight surgeonfishes (Acanthuridae) from the Indo-Pacific. Environmental Biology of Fishes 9(3/4): 193-223.

Sabater, M.G. and Carroll, B.P. 2009. Trends in Reef Fish Population and Associated Fishery after Three Millennia of Resource Utilization and a Century of Socio-Economic Changes in American Samoa. Reviews in Fisheries Science 17(3): 318 -335.

Sabater, M. G. and Tofaeono, S. 2007. Effects of scale and benthic composition on biomass and trophic group distribution of reef fishes in American Samoa. Pacific Science 61: 503-520.

Sabater, M.G. and Tofaeono, S.P. 2006. Spatial variation in biomass, abundance, and species composition of "key reef species" in American Samoa. A technical report submitted by the Key Reef Species Program to Department of Marine and Wildlife Resources (DMWR). This study is funded by the Sportfish Restoration Grant under Federal Aid of the US Fish and Wildlife Service. Department of Marine and Wildlife Resources (DMWR).